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Friday, 13 June 2008

How does a pulse oximeter work?

Pulse oximetry exploits a physics phenomenon: oxygenated haemoglobin absorbs different wavelengths of light than does deoxygenated haemoglobin. Actually this phenomenon is really common - the reason that leaves are green is that they reflect light in the 'green' wavelength back to us whilst absorbing most the rest of the light. Bricks do the same, except that for them they absorb most of the 'not-red' wavelengths of visible light, reflecting the remainer and thus rendering them red.

So one would almost expect that deoxygenated haemoglobin absorbs different wavelengths than oxygenated haemoglobin does (technically, it has a different 'absorption spectrum'). And it does. A pulse oximeter fires two wavelengths through our skin - red and infrared, which are each absorbed preferentially by one of the two species of haemoglobin under consideration. When these wavelengths travel through our capillaries, they are differentially absorbed in a ratio that corresponds to the ratio of oxygenated to deoxygenated haemoglobin. A computer does the calculations, and gives you the arterial saturation of the blood.

I am pleased with its performance and how user-friendly it is. The display is brightly lit and very readable. I can check my oxygen saturation and heart rate instantly. The resolution is excellent and I can see on a graph the strength of my pulse graphically. Buy Now at amazon.com Santamedical Fingertip Pulse Oximeter

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This is a site dedicated to interesting and sometimes complicated ideas - in the abstract. This is NOT a site from which to obtain medical advice for yourself, your family or your friends. When it comes to specific health problems, nothing can replace the dedicated attentions of a medical doctor.